The present invention relates to power driven fasteners, and more particularly to improved fasteners including drive sockets for power driven and hand operated applications.
In high volume mass production assembly lines, power drive tools are commonly maintained in continual rotation without stopping between the sequential fastener drive operations. Multilobular fastener sockets and drive tool systems have provided high efficiency in converting the applied force to driving torque as described in U.S. Pat. Nos. 3,584,667 and 4,269,246 particularly in comparison to earlier hexagonal pattern sockets as described, for example, in U.S. Pat. No. 2,777,353.
It is particularly important in the employment of continually rotating power drive tooling to achieve accurate alignment of the tool as the tool engages the fastener socket walls in order to reduce frictional and deformation damage to the socket and also to the tool. When the respective drive bearing surfaces of the tool and fastener sockets are not entirely or sufficiently engaged, the resulting "bouncing" impacts of the rotating drive tool against the misaligned fastener surfaces causes particularly severe damage. While the improvement in torque transmission is provided by multilobular socket and driver systems, it is important that all of the driver lobes enter the receiving socket flutes before any of the driver lobes drive against a respective socket lobe. Consequently, it is important to the integrity of the fastener and the secured joint as well as retarding wear of the drive tool and reducing damage to the fastener socket that the drive tool bit pass into the socket flutes and attain a proper axial depth of engagement therein before the driver bit lobes are brought into virtually simultaneous driving engagement with the respective drive impact wall surfaces of the socket lobes. Accordingly, the present invention provides an improved fastener socket which ensures sufficient depth of engagement by the drive tool bit before torque transmission.